The present invention relates to an interlayer insulating film for insulating interconnections from each other in a semiconductor device, and particularly to an interlayer insulating film for a semiconductor device which is used for a device process based on a design rule of 0.25 .mu.m or less.
The reduction in dielectric constant of an interlayer insulating film has been examined with requirements toward finer-line geometries, reduced power consumption and increased operating speed of a semiconductor device.
Low dielectric constant materials disclosed at present are of a type containing carbon atoms or fluorine atoms for reducing the dielectric constant thereof. The dielectric constant of such a material put in practical use is substantially in a range of from 1.5 to 2.5.
Examples of low dielectric constant materials containing carbon atoms include organic SOG (Spin On Glass), fluorocarbon polymer, polyimide, and polyparaxylylene. It is known that such a material is low in density because it contains carbon atoms as an alkyl group, and it is also known that the material is low in dielectric constant because the polarizability of molecules themselves is low. Such a material being low in dielectric constant has also a high heat resistance essential as the material for a semiconductor device. The heat resistances of organic SOG, polyimide, and fluorocarbon polymer and polyparaxylylene are due to a siloxane structure, imide bonding, and benzene ring, respectively.
On the other hand, silicon oxyfluoride (SiOF) is known as a low dielectric constant material containing fluorine atoms. This material is low in density because the Si--O--Si bonding is terminated with fluorine atoms, and is low in dielectric constant because the polarizability of fluorine itself is low. The material is of course excellent in heat resistance.
The above-described related art low dielectric constant film exerts adverse effect on the reliability of a semiconductor device as compared with a related art interlayer insulating film (silicon oxide) used for a semiconductor device. The low dielectric constant film made of SiOF being silicon oxide containing fluorine atoms is known to be relatively excellent in film quality; however, it is not sufficient yet in moisture resistance and in stability against fluorine. The organic material is also poor in heat resistance, oxygen plasma resistance and rigidity.